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Go Tricks - unpack slice to struct fields

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Published on Apr 22, 2021

1 min read

Use reflect, in this example, we only show to unpack an int slice to a struct whose fields are all int type.

package main

import (
    "errors"
    "fmt"
    "reflect"
)

type Location struct {
    X int
    Y int
    Z int
}

func (loc Location) String() string {
    return fmt.Sprintf("X: %d, Y: %d, Z: %d", loc.X, loc.Y, loc.Z)
}

func unpackIntSliceToStruct(slice []int, st interface{}) error {
    s := reflect.ValueOf(st).Elem()
    if s.Kind() != reflect.Struct {
        return errors.New("st must be a struct pointer")
    }
    l := s.NumField()
    if len(slice) != l {
        return errors.New("number of fields doesn't match")
    }
    for i := 0; i < l; i++ {
        f := s.FieldByIndex([]int{i})
        if f.CanAddr() {
            f.SetInt(int64(slice[i]))
        }
    }
    return nil
}

func main() {
    points := []int{1, 2, 3}
    loc := Location{}
    err := unpackIntSliceToStruct(points, &loc)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(loc)
}

Result:

X: 1, Y: 2, Z: 3
 
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